Fire alarm pull station enclosure

ABSTRACT

The invention relates to a fire alarm pull station enclosure. The enclosure includes a frame configured to enclose a pull lever. The frame has side walls, which define an open front and back. The frame has support means adjacent the open front for supporting a tempered glass pane between the side walls and over the open front. The tempered glass pane has a groove formed thereon. In an embodiment of the invention, the frame is rectangular and has an open bottom end and a cap secured to the top end. The invention also relates to the use of a grooved tempered glass pane as a front for a fire alarm pull station enclosure.

BACKGROUND OF THE INVENTION

(i) Field of the Invention

The present invention relates to a fire alarm pull station. In particular, the present invention relates to a fire alarm pull station enclosure that comprises a frame having an open front in which a grooved tempered pane of glass is supported. The invention further relates to the use of a tempered glass pane as a front of a fire alarm pull station enclosure.

(ii) Description of the Related Art

It is well known in the art of fire alarm safety devices to use breakable glass fronts in order to gain access to either fire extinguishers, fire hoses or fire alarm pull levers. Generally, there are two types of fire alarm pull stations on which all variations are based. The first “free lever” pull type employs a small glass rod of minimal diameter or a small pane of glass which is shattered upon pull lever activation. The pull lever is not enclosed by a pull station “box”. Edwards U.S. Pat. No. 2,083,324 issued Jun. 8, 1937 discloses such a fire alarm pull station in which an exposed pull lever contains a small pane of glass which is shattered upon activation of the pull lever in a downward fashion. The pane of glass only protects actuation of circuitry and does not prevent tampering with the lever.

The second “box enclosure” type has a pull lever enclosed within a rectangular or square box with a breakable glass front. The disadvantages of the free lever type of pull station, namely possible tampering with the pull lever due to unimpeded access, are substantially overcome by the use of the enclosed pull station. One gains access to the pull lever by shattering the glass front. This structure was introduced to alleviate concerns with the free lever type pull station through the encasement of the lever. Known box-type enclosures use ordinary annealed glass, which is easily broken, to form the glass front.

U.S. Pat. No. 5,868,477, issued to Decarie, teaches a fire alarm pull station enclosure having a box shaped frame with a front pane of standard annealed glass. This pane has one or more vertical score marks formed thereon. These vertical score marks cause the pane to controllably break when struck by a striker. The sections of glass formed by striking are intended to fall down and out through the bottom of the enclosure, to expose the fire alarm lever and permit its actuation. This fire alarm pull station enclosure suffers from certain disadvantages. One disadvantage is that the significant size of the sections of broken glass and the common occurrence of straight edges (a problem exacerbated by breakage along the scoring marks) render them useful as weapons. In short, such an enclosure may provide an improvised weapon associated with means for providing a significant distraction (the alarm itself). In addition, the sections of glass produced by striking may not fall cleanly through the open bottom of the enclosure, but may become jammed within the enclosure, making actuation of the lever hazardous to the user. This risk is magnified in that the user, having discovered a fire, will invariably be under stress and will try to operate the device as quickly as possible. It is a principal object of the present invention to improve upon these box-type fire alarm pull station enclosures.

Safety glass and, in particular, tempered glass is known. Tempered glass has a number of beneficial properties and, in particular, improved strength over annealed glass and corresponding improved breakage resistance. Tempered glass is therefore commonly used in applications where resistance to breakage is required. Some common applications, for example, are glass table tops, computer monitors, oven doors, and the rear windows of automobiles.

Heat-treated glass may be classified as fully tempered or heat-strengthened. Heat treating of glass creates an initial condition of surface and edge compression. Generally, this condition is achieved by heating glass and then cooling the surfaces rapidly. This leaves the central glass relatively hot compared to the surfaces. As the central glass cools, it forces the surfaces and edges into compression. This compression must be overcome prior to fracture. The safety feature of tempered glass comes from its strength and impact resistance and from a unique fracture pattern. When tempered glass breaks, the glass fractures into small, relatively harmless fragments generally without sharp edges. Instantaneous total fragmentation generally follows full penetration of the compression layer.

Within the context of this application, “tempered glass” includes both fully tempered glass and heat-strengthened glass having substantially the same fracture characteristics of fully tempered glass.

Due to the high strength and impact resistance of tempered glass, to the inventor's knowledge it is not used in applications where easy breakage of a glass component may be required.

It is an object of the invention to obviate or mitigate at least one of the above-mentioned disadvantages of the prior art.

SUMMARY OF THE INVENTION

The disadvantages of the prior art may be overcome by providing an improved box type apparatus to allow quick access to the pull lever, in which the user can actuate the pull lever without the danger of large glass fragments, either stuck within the enclosure where they can present a risk of harm to the user, or otherwise in the vicinity where they may be used as an improvised weapon.

The present inventor surprisingly and unexpectedly discovered that a grooved tempered glass pane could be used as a front for a fire alarm pull station enclosure. Surprisingly this arrangement provides acceptable strength for the application (i.e. the pane can be broken through the application of reasonable striking force by a user) while imparting the beneficial fracture pattern described above.

The fire alarm pull station in its broad aspect comprises: a frame configured to enclose a pull lever, the frame having side walls defining an open front; a tempered glass pane having a groove formed thereon; the frame having supports adjacent the open front for supporting the tempered glass pane between the side walls and over the open front.

In another broad aspect the invention comprises the use of a grooved tempered glass pane as a front for a fire alarm pull station enclosure.

In a preferred embodiment, the frame is rectangular in shape and is open at the bottom end allowing for glass particles to fall through when the device is employed and the tempered glass is broken. (Alternatively, means for collecting the glass fragments may be provided at the base of the enclosure.) Preferably, in use, the frame is secured to a mounting surface (typically, a wall) wherein a pull lever is attached in such a way that the frame fully encloses the pull lever. In a preferred embodiment, the frame is made of metal and, more preferably, a sheet steel alloy. There may be attached to the outside of one of the sides of the frame a tether. At the end of the tether is a striking device which can be used to break the tempered glass pane and gain access to the pull lever.

In a preferred embodiment of the present invention, the tempered glass is provided with a groove, suitably having an angle of between 30 degrees and 60 degrees relative to the surface of the tempered glass pane on which it is formed. More preferably, the groove has an angle of between about 40 degrees and 50 degrees relative to the surface of the tempered glass pane on which it is formed. Most preferably, the groove has an angle of about 45 degrees relative to the surface of the tempered glass pane on which it is formed. In a preferred embodiment, the groove penetrates about half the thickness of the tempered glass pane. This groove permits breakage of the tempered glass upon striking of the glass by a user with a reasonable amount of force.

According to another aspect of the present invention, there is provided supports for the tempered glass pane. In a preferred embodiment, the frame is rectangular and has a pair of spaced-apart parallel side walls, each having supports. Preferably, the supports include two detents which support the tempered glass pane at its two lower corners. The detents act as support, along with slots on the parallel side walls. Upon striking and fracturing of the glass pane, the glass pane collapses and glass fragments are released. Preferably, the fragments fall through an open bottom of the frame.

BRIEF DESCRIPTION OF THE DRAWINGS

Drawings which illustrate embodiments of the present invention will now be described, by way of example only, with reference to the attached Figures, wherein:

FIG. 1 is an exploded perspective view of an embodiment of a fire alarm pull station enclosure of the present invention;

FIG. 2 is a horizontal section facing downwardly showing the slot and detent support and the grooved tempered pane of the fire alarm pull station enclosure of FIG. 1;

FIG. 2 a is an enlarged fragmentary view of the groove of FIG. 2;

FIG. 3 is an enlarged fragmentary perspective view illustrating in detail the slot and detent support for the tempered glass pane;

FIG. 4 is a perspective view of the assembled fire alarm pull station in use showing the fragmented tempered glass breakage; and

FIG. 5 is a front elevation of the fire alarm pull station shown in FIG. 4 following tempered glass pane breakage.

DETAILED DESCRIPTION OF THE INVENTION

FIGS. 1-5 illustrate an embodiment of the pull station enclosure of the invention which comprises open-back box enclosure 10 which is screwed to a mounting surface, generally a support wall, so as to encase within the box the fire alarm pull lever 19 (FIG. 5). The enclosure 10 is preferably of rectangular shape and comprises a frame 11 consisting of a pair of spaced-apart parallel side walls 12, 14 joined at the rear edges thereof at the top and bottom by connecting strips 16, 18 respectively, which may be formed integral therewith. Enclosure 10 may be secured to a mounting surface by any suitable means. In a preferred embodiment, screw holes 20 formed in strips 16, 18 permit securement of enclosure 10 to a support wall by screws 13 (FIG. 5). Opening 22 defined between side walls 12, 14 and strips 16, 18 is sufficiently large to receive pull lever 19. Preferably, the front edges of side walls 12, 14 have inwardly facing flanges 24, 26 for reasons which will become apparent as the description proceeds. A front bottom plate 28 secured to flanges 24, 26 such as by spot welding has holes 30 formed therein in alignment with holes 20 in rear bottom strip 18 to allow insertion of a screw driver for driving screws through holes 20.

A cap 31 having end flanges 32, 34 and front and rear flanges 36, 38 is preferably secured to side walls 12, 14 at the top thereof by screws 40 passing through end flanges 32, 34. With regard to end flanges 32,34, it may be necessary to angle the front edge of one or both of end flanges 32, 34 (as shown) to accommodate certain glass thicknesses. Each of side walls 12, 14 has an upstanding inner rib 42, 44 bent rearwardly at an angle of about 45 degrees to the plane of front flanges 24, 26 from elongated plates 43, 45 attached thereto such as by spot welding along their length at a uniform distance from front flanges 24, 26 respectively to receive the side edges of glass pane 46 in slots 47 defined between front flanges 24,26 and inner ribs 42,44. A detent 50, such as a rivet passing through side walls 12, 14, closes the bottom of slots 47. Flanges 42 and 44 can be crimped at their bases to form a detent, not shown, to close the bottoms of slots 47.

In assembly, mounting screws 13 are driven through upper and lower screw holes 20 to secure frame 11 to a supporting wall. Tempered glass pane 46 is inserted from above in slots 47 defined between front flanges 24, 26 and ribs 42, 44 and is supported at its lower corners by shallow detent 50 projecting from side walls 12, 14 into slots 47. Closure cap 31 is then attached to side walls 12, 14 by screws 40, whereby cap front flange 36, side wall flanges 24, 26, and bottom plate 28 conceal the edges of tempered glass pane 46.

Tempered glass pane 46 has at least one groove 52 formed thereon. Preferably, groove 52 is formed vertically on the inner surface of pane 46 (i.e. the surface that will face the mounting surface) substantially along the length thereof. Preferably, groove 52 has an angle between about 30 degrees and 60 degrees relative to the surface of the glass on which it is formed. More preferably, groove 52 has an angle of between about 40 degrees and 50 degrees relative to the surface of the glass on which it is formed. Most preferably, groove 52 has an angle of about 45 degrees relative to the surface of the glass on which it is formed. Preferably, the groove penetrates about half the thickness of the tempered glass pane. The depth of the groove must be sufficiently deep to permit easy glass breakage, but is constrained in that if the groove penetrates too deeply the pane may shatter. A suitable groove width is between about 1/16 of an inch and about 3/32 of an inch.

While in a preferred embodiment a single vertical groove is shown, other arrangements are possible. The groove may, for example, be formed horizontally or at an angle on glass pane 46. It is also possible to have a plurality of grooves, and a plurality of grooves may be necessary where the length of a single groove is constrained by the dimensions of the frame, such that the single groove does not provide the requisite ease of breakage (i.e. such might be the case where a horizontal groove is formed on a pane of limited width.) As will be apparent to a person skilled in the art, however, a single groove is preferred because it is less labour intensive and so more cost efficient than multiple grooves. In a preferred embodiment, a single vertical groove 52 is formed on pane 46. On a pane having dimensions of about 4 inches by about 6½ inches, which is suitable for a typical frame having a width of about 4½ inches by about 7 inches, a single vertical groove 52 of about 4½ inches is suitable. Preferably, groove 52 is centrally located on pane 46. Suitable positions and dimensions of the groove may be readily ascertained by a person skilled in the art.

To manufacture grooved tempered glass pane 46, a tempered glass pane of suitable size can be purchased or manufactured according to methods commonly known in the art. Preferably glass pane 46 has a thickness between about ⅛ inches and 3/16 inches. The depth of groove 52 is preferably between about 1/16 inches and 3/32 inches. A diamond blade tool is suitably used for cutting groove 52. Groove 52 is preferably cut in water, which the inventor has found reduces chance of fracture during the cutting process. Groove 52 may be suitably cut at a temperature of between 70° and 72° Fahrenheit (between about 21° and 22.5° Celsius). Pane 46 can further be dried at a temperature of 68° to 70° Fahrenheit (between about 20° and 21° Celsius.).

A striker 60 attached to a side wall by a tether 62, such as a cable or chain, can be conveniently used by an operator to strike tempered glass pane 46 which is rendered frangible by groove 52 to break it. Preferably, striker 60 and tether 62 are positioned on the right hand side of enclosure 10 when installed on a mounting surface due to the fact that a majority of users are likely to be right-handed. The broken pane of glass 46 falls through the open bottom of enclosure 10 in the form of small fragments 46 a, thereby rendering the pull lever accessible. In an alternate embodiment, a trap (not shown) may be provided to receive fragments 46 a.

The present invention provides a number of advantages. The fire alarm pull station cover maintains the desired result of protecting the pull lever from easy access tampering or accidental actuation, while the groove permits the breakage of the tempered pane of glass.

It will be understood that modifications can be made in the embodiment of the invention illustrated and described herein without departing from the scope and purview of the invention as defined by the appended claims.

In particular, and without limiting the generality of the foregoing, it will be understood that the specific shape and configuration of the frame and the means of supporting the tempered glass pane may be changed without departing from the scope of the invention. Further, a worker skilled in the art will understand that the enclosure may be attached to the mounting surface using any suitable fasteners such as nails, adhesives, or may even be integrally formed with the mounting surface and the attachment means described herein are merely described for illustrative purposes. 

1. A fire alarm pull station enclosure comprising: a frame configured to enclose a pull lever, the frame having side walls defining an open front; a tempered glass pane having a groove formed thereon; the frame having supports adjacent the open front for supporting the tempered glass pane between the side walls and over the open front.
 2. A fire alarm pull station enclosure as claimed in claim 1, wherein the tempered glass pane has opposite side edges and bottom corners and each of the supports comprises an inwardly facing vertical slot on one of the side walls adjacent the open front for receiving and laterally supporting a side edge and a detent at the bottom of each slot for engaging and vertically supporting a bottom corner.
 3. A fire alarm pull station enclosure as claimed in claim 2 in which each of the side walls has an inwardly facing front flange defining sides of the open front, and an inwardly facing rib formed on each of the side walls defining with the front flange one of the vertical slots.
 4. A fire alarm pull station enclosure as claimed in claim 3 in which each of the detents comprises an inwardly projecting stud attached to the side wall and extending into the slot to engage a bottom corner of the tempered glass pane.
 5. A fire alarm pull station enclosure as claimed in claim 3 in which the inwardly facing rib is a flange formed on an elongated metal strip attached to the side wall.
 6. A fire alarm pull station enclosure as claimed in claim 5 in which the flange is bent rearwardly to define an angle of about 45 degrees to the side wall.
 7. A fire alarm pull station enclosure as claimed in claim 2, wherein the frame is formed of metal.
 8. A fire alarm pull station enclosure as claimed in claim 2, wherein the frame has an open bottom and back.
 9. A fire alarm pull station enclosure as claimed in claim 8, further comprising a removable cap mounted on the side walls.
 10. A fire alarm pull station enclosure as claimed in claim 9 in which the removable cap is secured to the frame by screws.
 11. A fire alarm pull station enclosure as claimed in claim 1, additionally comprising a striker and an elongated tether for attaching the striker to the frame.
 12. A fire alarm pull station enclosure as claimed in claim 11, wherein the tether is a cable.
 13. A fire alarm pull station enclosure as claimed in claim 11, wherein the striker also functions as a secondary lever for actuation of a pull lever of the fire alarm pull station.
 14. A fire alarm pull station enclosure as claimed in claim 8, further comprising means for attaching the frame to a mounting surface.
 15. A fire alarm pull station enclosure as claimed in claim 14 in which the means for attaching the frame to a mounting surface comprises upper and lower metal strips connecting the side walls adjacent the back of the side walls and defining with the side walls the open back, said metal strips having a plurality of apertures therein for receiving screws.
 16. A fire alarm pull station as claimed in claim 1, wherein the tempered glass pane has a plurality of grooves formed thereon.
 17. A fire alarm pull station as claimed in claim 7, wherein the frame is substantially rectangular in shape.
 18. A fire alarm pull station as claimed in claim 8, wherein the groove is vertically disposed on the pane of glass.
 19. A fire alarm pull station enclosure as claimed in claim 1, wherein the groove penetrates up to about half the thickness of the tempered glass pane.
 20. A fire alarm pull station enclosure as claimed in claim 8, wherein the groove penetrates up to about half the thickness of the tempered glass pane.
 21. A fire alarm pull station enclosure as claimed in claim 18, wherein the groove penetrates up to about half the thickness of the tempered glass pane.
 22. A fire alarm pull station enclosure as claimed in claim 20, wherein the tempered glass pane has a thickness of between about ⅛ of an inch and about 3/16 of an inch and the groove penetrates to a depth of between about 1/16 of an inch and about 3/32 of an inch.
 23. A fire alarm pull station enclosure as claimed in claim 19, wherein the groove has an angle of between about 30 degrees and 60 degrees relative to the surface of the tempered glass pane on which it is formed.
 24. A fire alarm pull station enclosure as claimed in claim 20, wherein the groove has an angle of between about 30 degrees and 60 degrees relative to the surface of the tempered glass pane on which it is formed.
 25. A fire alarm pull station enclosure as claimed in claim 21, wherein the groove has an angle of between about 30 degrees and 60 degrees relative to the surface of the tempered glass pane on which it is formed.
 26. A fire alarm pull station enclosure as claimed in claim 19, wherein the groove has an angle of between about 40 degrees and 50 degrees relative to the surface of the tempered glass pane on which it is formed.
 27. A fire alarm pull station enclosure as claimed in claim 19, wherein the groove has an angle of 45 degrees relative to the surface of the tempered glass pane on which it is formed.
 28. The use of a grooved tempered glass pane as a front for a fire alarm pull station enclosure. 